1. Field of the Invention
The present invention relates to a pressure sensor to be assembled by mutually engaging a sensor housing formed of metal, and a connector housing mainly formed of synthetic resin.
2. Discussion of the Related Art
One example of such a pressure sensor mentioned above, disclosed in Japanese Patent Application Laid-Open Publication No. 209115/1995, titled xe2x80x9cSEMI-CONDUCTOR TYPE PRESSURE SENSOR AND MANUFACTURING METHOD THEREFOR,xe2x80x9d is generally known.
Referring to FIG. 10, there is shown a section of a pressure sensor 900 constructed according to the conventional technology described in the above publication. As shown in FIG. 10, the conventional technology permits the pressure sensor 900 to be assembled by effecting so called caulking (i.e., curling) directly on a connector housing 1 (formed of synthetic resin) in which terminal pins 2a, 2b and the like have been insert-molded. The caulking is performed by curling a projecting portion or one of two end portions of a sensor housing 3 (formed of metal), resulting in juncture and fixed engagement of the connector and sensor housing 1, 3.
However, the conventional pressure sensor, which is to be assembled by the caulking performed directly on the connector housing 1, suffers from the following problems:
(Problem1)
When the caulking is performed for assembling the pressure sensor 900, the junction of the connector housing 1 formed of synthetic resin and the sensor housing 1, which junction means an abutment surface of the connector housing 1 on which the projecting portion or the one end portion of the connector housing 3 abuts, is subjected to an excessively large stress thereon, leading to a likelihood of undesired deformation or failure of the connector housing 1.
(Problem 2)
Since the connector housing 1 confines a fluid 13 of high-pressure in a fluid-tight manner, the junction of connector housing 1 with the sensor housing 3 is, in operation of the pressure sensor 900, subjected to a large compressive stress thereon, unexpectedly resulting in deformation or deflection of the connector housing 1 at the above junction thereof.
One of possible solutions to those problems is, for instance, to design the connector housing 1 so as to have an increased area for the junction of the connector housing 1. However, this solution would increase the total size of a pressure sensor, meaning that downsizing thereof would be prevented.
It is therefore an object of the present invention to provide a pressure sensor which is available even under high pressure and which is capable of being downsized.
This object indicated above may be achieved according to any one of the following modes of this invention. Each of these modes of the invention is numbered like the appended claims, and depends from the other mode or modes, where appropriate. This type of explanation about the present invention is for better understanding of some ones of a plurality of technical feats and a plurality of combinations thereof disclosed in this specification, and dose not mean that the plurality of technical features and the plurality of combinations in this specification are interpreted to encompass only the following modes of this invention:
(1) A pressure sensor including a sensor housing formed of metal, and a connector housing mainly formed of synthetic resin. The connector housing includes a shoulder portion thereof in the form of a metal plate having an inner and an outer periphery thereof, on which shoulder portion a juncture of the sensor and connector housing is formed as a result of joining the sensor and connector housing by curling a projecting portion or one of two end portions of the sensor housing toward the shoulder portion. Further, the curling is performed under engagement of the sensor and connector housing therebetween, for assembling the pressure sensor.
In the pressure sensor according to this mode (1), the shoulder portion of the connector housing functioning as the junction of the connector housing with the sensor housing is constructed by the metal plate. As a result, the strength of pressure resistance of the pressure sensor is increased, preventing the connector housing from being unexpectedly deformed or failed when manufactured. The increase in the strength of pressure resistance of the pressure sensor would also eliminate a likelihood of undesired deformation and deflection of the connector housing, leading to availability of the pressure sensor even in high-pressure environment.
In the pressure sensor according to this mode (1), the term xe2x80x9cconnector housingxe2x80x9d may be interpreted to mean a sub-housing of the pressure sensor for accommodating at least one external connector, and the term xe2x80x9csensor housingxe2x80x9d may be interpreted to mean another sub-housing of the pressure sensor for receiving a fluid, a pressure of which is to be measured by the pressure sensor. It is not indispensable in practicing the present invention, to configure the sensor housing to accommodate a pressure-sensitive element
In the pressure sensor according to this mode (1), the term xe2x80x9cinner periphery of the metal platexe2x80x9d can be called a xe2x80x9cthrough holexe2x80x9d for permitting a terminal pin to be passed therethrough.
(2) The pressure sensor according to the above mode (1), wherein the metal plate is generally shaped as a ring.
(3) The pressure sensor according to the above mode (1) or (2), wherein the sensor housing is coaxially fitted with the connector housing, wherein the metal plate includes one reference line intersecting a plane of the metal plate, and wherein the metal plate is fitted with the connector housing such that the connector housing extends substantially parallel to the reference line.
(4) The pressure sensor according to any one of the above modes (1)-(3), wherein the junction of the sensor and connector housing is located on an edge of the shoulder portion of the connector housing, which edge is formed so as to include, on a cross-section obtained by hypothetically cutting the shoulder portion by a reference plane perpendicular to a plane of the metal plate, at least one of a curved line, a straight line intersecting the plane of the metal plate, and a stepped line.
The pressure sensor according to this mode (4) would enable an area of a surface on which a contact of the shoulder portion of the connector with the sensor housing is performed, to be easily increased as compared with the case of a metal plate having a flat end face thereof. The increase in the contacting area contributes to even distribution of pressures acting on a portion of the connector housing which is contacted with one of two end faces of the metal plate, meaning that the strength of pressure resistance of the pressure sensor is improved.
(5) The pressure sensor according to any one of the above modes (1)-(4), wherein the connector housing is integrally formed together with the metal plate.
The pressure sensor according to this mode (5) would permit a reduction in the manufacturing time thereof, and would also permit close engagement between the metal plate and the remainder of the connector housing which is formed of synthetic resin. The close engagement between the metal plate and the remainder of the connector housing would, for example, facilitate to downsize the pressure sensor, and to increase the strength of the pressure resistance of the pressure sensor.
(6) The pressure sensor according to the above mode (5), wherein the connector housing is formed by a process in which the metal plate is inserted into a mold for molding the connector housing, prior to the molding, and then a mass of raw synthetic resin is fed into the mold and is thereafter hardened.
(7) The pressure sensor according to any one of the above modes (1)-(6), wherein the metal plate is fitted with the connector housing unremovably therefrom, by holing the metal plate by two opposing portions of the connector housing which cooperate to cause the metal plate to be interposed therebetween.
(8) The pressure sensor according to any one of the above modes (1)-(7), wherein the inner periphery of the metal plate is formed so as to extend, on a cross-section obtained by hypothetically cutting the metal plate by one reference plane substantially perpendicular to a direction in which pressure to be measured by the pressure sensor acts therein, to form one closed line other than a true circle.
In the pressure sensor according to this mode (8), the inner periphery of the metal plate is formed so as to extend on the cross-section of the metal plate along the closed line other than a true circle. On the other hand, in general, a space formed in the inner periphery of the metal plate is intended for permitting at least one conductor to be passed through the inner periphery.
Therefore, the pressure sensor according to this mode (8) would permit the metal plate to be configured so as to avoid the inner periphery to have an excessive dimension, owing to the flexibility in shape of the cross-section of the inner periphery. The avoidance of the excessively increased size of the inner periphery permits an increase in area of a surface on which a contact of the metal plate with the remainder of the connector housing is performed. The increased contacting area leads to an increased seating area in which the remainder of the connector housing, formed of synthetic resin, is to be seated on a surface of the metal plate, and eventually leads to a reduced compressive stress acting on the synthetic resin. The reduced compressive stress permits the pressure sensor to be available even under high-pressure.
In the pressure sensor according to this mode (8), the acceptance of the closed line other than a true circle as the cross-sectional shape of the inner periphery would also permit the length of the closed line to be longer than the true circle.
On the other hand, there is formed an annular portion within a bearing part of the synthetic resin of the connector housing. The bearing part bears a shearing stress produced in operation of the pressure sensor, and the bearing part is, for example, located between the metal plate and the sensor housing. The annular portion extends substantially parallel to a direction in which the sharing stress acts within the bearing part of the connector housing.
To refer to the relationship in length between the closed line mentioned above, and a circumference of a transversal section of the annular portion mentioned above, the longer the closed line, the longer the circumference.
Additionally, the longer the above circumference of the transversal section of the annular portion, the smaller the sharing stress of the above bearing part of the connector housing. The small sharing stress eliminates a necessity to design the connector housing so as to have the bearing part of a longer dimension for reducing the sharing stress of the bearing part. The elimination of the necessity in designing dimension permits the bearing part to have a reduced thickness thereof, enabling the pressure sensor to be downsized.
(9) The pressure sensor according to the above mode (8), wherein the inner periphery of the metal plate includes at least one of a convex projecting from the true circle outwardly thereof, and a concave projecting from the true circle inwardly thereof.
(10) The pressure sensor according to the above mode (8) or (9), wherein the metal plate is fitted with the connector housing such that a space formed in the inner periphery of the metal plate is filled with the synthetic resin of the connector housing.
(11) The pressure sensor according to any one of the above modes (8)-(10), wherein the connector housing includes a connecting portion thereof with which a connector is to be connected, from which connecting portion at least one conductor extends passing through the inner periphery of the metal plate toward the sensor housing.
(12) The pressure sensor according to the above mode (11), wherein the inner periphery of the metal plate is configured to have a necessary and sufficient dimension permitting the at least one conductor to pass through the inner periphery of the metal plate.
(13) The pressure sensor according to any one of the above modes (1)-(12), wherein the metal plate is formed such that at least one of a continued groove, ridge and stepped portion extends along the entire circumferential length of at least one of the inner and outer periphery of the metal plate, with a corresponding portion of the connector housing fitted with the at least one of the continued groove, ridge and stepped portion.
In the pressure sensor according to this mode (13), the metal plate is so formed as to have a projecting circumferential portion thereof in relation to a portion of the metal plate adjacent to the projecting circumferential portion, due to the presence of the at least one of the continued groove, ridge and stepped portion of the metal plate. The projecting circumferential portion of the metal plate can be tightly interposed by two portions of the connector housing opposing to each other in a direction in which pressure to be measured by the pressure sensor acts therein, together with of a portion of the connector housing which is integrally formed with the above two opposing portions and which is adjacent to the projecting circumferential portion of the metal plate in a direction intersecting the above acting direction of pressure to be measured.
On the other hand, the amount of shrinkage of an object made of synthetic resin is larger than that of an object made of metal, in general.
Consequently, in the pressure sensor according to this mode (13), at least in the event where the above projecting circumferential portion of the metal plate is disposed at the proximity of the sensor housing, the amount of a sink of a portion of the connector housing adjacent to one of two end faces of the metal plate which is closer to the sensor housing than the other end face would be reduced, after the connector housing has been integrally formed in the presence of the metal plate. Wherein, the sink, which occurs due to an increase in shrinkage of the synthetic resin with a drop in the temperature of the synthetic resin, causes a gap between the one end face of the metal plate and the adjacent portion of the connector housing.
Owing to this fact, when the pressure sensor according to this mode (13) is installed in a vehicle or the like, fatigue of a metal component of the connector housing (e.g., a bonding wire for bonding a pressure-sensitive element and a conductor both disposed within the connector housing), which fatigue is to result from vibration of the connector housing due to the gap between the one end face of the metal plate and the adjacent portion of the connector housing, would be eliminated, leading to an improvement in reliability and durability of the pressure sensor.
(14) The pressure sensor according to the above mode (13), wherein the connector housing is integrally formed together with the metal plate, and wherein the at least one of the continued groove, ridge and stepped portion of the metal plate is disposed at the proximity of one of two end faces of the metal plate which is closer to the sensor housing than the other end face.
(15) A pressure sensor including a sensor housing formed of metal, and a connector housing mainly formed of synthetic resin. The connector housing includes a shoulder portion thereof in the form of a metal plate having an inner and an outer periphery thereof, on which shoulder portion the connector housing is engaged with the sensor housing, for assembling the pressure sensor. Further, a junction of the sensor and connector housing is located on an edge of the shoulder portion of the connector housing, which edge is formed so as to include, on a cross-section obtained by hypothetically cutting the shoulder portion by a reference plane perpendicular to a plane of the metal plate, at least one of a curved line, a straight line intersecting the plane of the metal plate, and a stepped line.
Wherein a junction of the sensor and connector housing is located on an edge of the shoulder portion of the connector housing, which edge is formed so as to include, on a cross-section obtained by hypothetically cutting the shoulder portion by a reference plane perpendicular to a plane of the metal plate, at least one of a curved line, a straight line intersecting the plane of the metal plate, and a stepped line.
The pressure sensor according to this mode (15) would enable an area of a surface on which a contact of the shoulder portion of the connector with the sensor housing is performed, to be easily increased as compared with the case of a metal plate having a flat end face thereof. The increase in the contacting area contributes to even distribution of pressures acting on a portion of the connector housing which is contacted with one of two end faces of the metal plate, meaning that the strength of pressure resistance of the pressure sensor is improved.
(16) A pressure sensor including a sensor housing formed of metal, and a connector housing mainly formed of synthetic resin. The connector housing includes a shoulder portion thereof in the form of a metal plate having an inner and an outer periphery thereof, on which shoulder portion the connector housing is engaged with the sensor housing, for assembling the pressure sensor. Further, the connector housing is integrally formed together with the metal plate.
The pressure sensor according to this mode (16) would permit a reduction in the manufacturing time thereof; and would also permit close engagement between the metal plate and the remainder of the connector housing which is formed of synthetic resin. The close engagement between the metal plate and the remainder of the connector housing would, for example, facilitate to downsize the pressure sensor, and to increase the strength of the pressure resistance of the pressure sensor.
(17) The pressure sensor according to the above mode (16), wherein the connector housing is formed by a process in which the metal plate is inserted into a mold for molding the connector housing prior to the molding, and then a mass of raw synthetic resin is fed into the mold and is thereafter hardened.
(18) A pressure sensor including, a sensor housing formed of metal, and a connector housing mainly formed of synthetic resin. The connector housing includes a shoulder portion thereof in the form of a metal plate having an inner and an outer periphery thereof, on which shoulder portion the connector housing is engaged with the sensor housing, for assembling the pressure sensor. Further, the inner periphery of the metal plate is formed so as to extend, on a cross-section obtained by hypothetically cutting the metal plate by one reference plane substantially perpendicular to a direction in which pressure to be measured by the pressure sensor acts therein, to form one closed line other than a true circle.
In the pressure sensor according to this mode (18), the inner periphery of the metal plate is formed so as to extend on the cross-section of the metal plate along the closed line other than a true circle. On the other hand, in general, a space formed in the inner periphery of the metal plate is intended for permitting at least one conductor to be passed through the inner periphery.
Therefore, the pressure sensor according to this mode (18) would permit the metal plate to be configured so as to avoid the inner periphery to have an excessive dimension, owing to the flexibility in shape of the cross-section of the inner periphery. The avoidance of the excessively increased size of the inner periphery permits an increase in area of a surface on which a contact of the metal plate with the remainder of the connector housing is performed. The increased contacting area leads to an increased seating area in which the remainder of the connector housing, formed of synthetic resin, is to be seated on a surface of the metal plate, and eventually leads to a reduced compressive stress acting on the synthetic resin. The reduced compressive stress permits the pressure sensor to be available even under high-pressure.
In the pressure sensor according to this mode (18), the acceptance of the closed line other than a true circle as the cross-sectional shape of the inner periphery would also permit the length of the closed line to be longer than the true circle.
On the other hand, there is formed an annular portion within a bearing part of the synthetic resin of the connector housing. The bearing part bears a shearing stress produced in operation, and the bearing part is, for example, located between the metal plate and the sensor housing. The annular portion extends substantially parallel to a direction in which the sharing stress acts within the bearing part of the connector housing.
To refer to the relationship in length between the closed line mentioned above, and a circumference of a transversal section of the annular portion mentioned above, the longer the closed line, the longer the circumference.
Additionally, the longer the above circumference of the transversal section of the annular portion, the smaller the sharing stress of the above bearing part of the connector housing. The small sharing stress eliminates a necessity to design the connector housing so as to have the bearing part of a longer dimension for reducing the sharing stress of the bearing part. The elimination of the necessity in designing dimension permits the bearing part to have a reduced thickness thereof, enabling the pressure sensor to be downsized.
(19) The pressure sensor according to the above mode (18), wherein the inner periphery of the metal plate includes at least one of a convex projecting from the true circle outwardly thereof, and a concave projecting from the true circle inwardly thereof.
(20) The pressure sensor according to the above mode (18) or (19), wherein the metal plate is fitted with the connector housing such that a space formed in the inner periphery of the metal plate is filled with the synthetic resin of the connector housing.
(21) The pressure sensor according to any one of the above modes (18)-(20), wherein the connector housing includes a connecting portion thereof with which a connector is to be connected, from which connecting portion at least one conductor extends passing through the inner periphery of the metal plate toward the sensor housing.
(22) The pressure sensor according to the above mode (21), wherein the inner periphery of the metal plate is configured to have a necessary and sufficient dimension permitting the at least one conductor to pass through the inner periphery of the metal plate.
(23) A pressure sensor including a sensor housing formed of metal, and a connector housing mainly formed of synthetic resin. The connector housing includes a shoulder portion thereof in the form of a metal plate having an inner and an outer periphery thereof, on which shoulder portion the connector housing is engaged with the sensor housing, for assembling the pressure sensor. Further, the metal plate is formed such that at least one of a continued groove, ridge and stepped portion extends along the entire circumferential length of at least one of the inner and outer periphery of the metal plate, with a corresponding portion of the connector housing fitted with the at least one of the continued groove, ridge and stepped portion.
In the pressure sensor according to this mode (23), the metal plate is so formed as to have a projecting circumferential portion thereof in relation to a portion of the metal plate adjacent to the projecting circumferential portion, due to the presence of the at least one of the continued groove, ridge and stepped portion of the metal plate. The projecting circumferential portion of the metal plate can be tightly interposed by two portions of the connector housing opposing to each other in a direction in which pressure to be measured by the pressure sensor acts therein, together with a portion of the connector housing which is integrally formed with the above two opposing portions and which is adjacent to the projecting circumferential portion of the metal plate in a direction intersecting the above acting direction of pressure to be measured.
On the other hand, the amount of shrinkage of an object made of synthetic resin is larger than that of an object made of metal, in general.
Consequently, in the pressure sensor according to this mode (23), at least in the event where the above projecting circumferential portion of the metal plate is disposed at the proximity of the sensor housing, the amount of a sink of a portion of the connector housing adjacent to one of two end faces of the metal plate which is closer to the sensor housing than the other end face would be reduced, after the connector housing has been integrally formed in the presence of the metal plate. Wherein, the sink, which occurs due to an increase in shrinkage of the synthetic resin with a drop in the temperature of the synthetic resin, causes a gap between the one end face of the metal plate and the adjacent portion of the connector housing.
Owing to this fact, when the pressure sensor according to this mode (23) is installed in a vehicle or the like, fatigue of a metal component of the connector housing (e.g., a bonding wire for bonding a pressure-sensitive element and a conductor both disposed within the connector housing), which fatigue is to result from vibration of the connector housing due to the gap between the one end face of the metal plate and the adjacent portion of the connector housing, would be eliminated, leading to an improvement in reliability and durability of the pressure sensor.
(24) The pressure sensor according to the above mode (23), wherein the connector housing is integrally formed together with the metal plate, and wherein the at least one of the continued groove, ridge and stepped portion of the metal plate is disposed at the proximity of one of two end faces of the metal plate which is closer to the sensor housing than the other end face.